Recently, an automatic clutch system has been developed which uses a gear type transmission for manual transmission and automates operation of a clutch which is a friction mechanism. Further, an automated manual transmission (hereinafter abbreviated as “automated MT”) has also been developed which automates operations of a clutch and a synchromesh mechanism.
The automatic clutch and the automated MT respectively launch a vehicle by gradually engaging a clutch that connects and disconnects torque of an engine which is a driving power source. Further, when a transmission starts, the automated MT disengages the clutch that connects and disconnects torque of an engine which is a driving power source, switches the synchromesh mechanism, and then engages the clutch again. In general, a dry single disc clutch is used for the clutch that connects and disconnects torque of an engine which is a driving power source. The dry single disc clutch is equipped with a diaphragm spring that generates a force to push the clutch toward the disc and keep the engagement of the clutch.
Conventionally, when the key switch is turned off while the synchromesh mechanism is engaged, power supply to the clutch actuator is shut off and the clutch is engaged. As the result, the vehicle runs off. To avoid this, an automatic neutral technology has been known which neutralizes the synchromesh mechanism and engages the clutch. (For example, see Japanese Patent 3501881)
Further, an actuator structure using an electric motor and a worm gear has been well known. (For example, see Japanese Patent Laid-open No. Sho 60 (1985)-256671, Japanese Patent Laid-open No. 2004-68878) The worm gear has a self-locking property and can keep the clutch disengaged after power supply to the electric motor is shut off. Therefore, the actuator of a self-locking property can prevent the clutch from being engaged by shut-off of power supply to the actuator when the key switch is turned off.